The controversial Mid-Barataria Sediment Diversion, a massive $3 billion coastal restoration project tied up in lawsuits, may hit yet another roadblock.

A new scientific review may be in order to determine whether “forever chemicals” – PFAS compounds – pose a threat to endangered species in the Barataria Basin if the project is built. While scientists suggest the issue likely does not pose a problem, a full review would require more time, potentially further delaying the project and adding costs.

Indeed, the project may in fact lessen endangered species' exposure to the chemicals because of water being diverted out of the river to build land, the scientists say.

Nonetheless, scientists with both the National Marine Fisheries Service and the U.S. Fish & Wildlife Service say new research into the chemicals, combined with the rapid expansion of Environmental Protection Agency rules aimed at removing them from drinking water, is enough to trigger a rewrite of both agencies’ biological opinions that declared the diversion was safe to endangered species.

Already studied and analyzed for years, the diversion near Ironton would transfer up to 75,000 cubic feet per second of Mississippi River water and sediment into the Barataria Basin for about six months each year, representing about 5.6% of the river’s annual flow. It is expected to build about 21 square miles of land during its first 50 years of operation.

Per- and polyfluoroalkyl substances – known as PFAS -- are dubbed "forever chemicals" because they do not naturally break down and remain toxic for generations. PFAS have been used to make non-stick coatings on cookware and protective coatings for carpets and fabrics, in coatings for paper and cardboard food packaging, firefighting foams, ski wax, and other products. They've been found in water throughout the country, including the Mississippi River.

Both of those September requests, filed with the federal-state Louisiana Trustee Implementation Group that recommended BP Deepwater Horizon oil spill fine money be used to build the project, came after a January lawsuit filed by opponents of the diversion. The lawsuit cited the forever chemicals as a reason to halt construction of the project.

However, the letters submitted by the two federal agencies also said initial information indicates the chemicals are not expected to be a threat because they’re likely to drop out of Mississippi River water long before that water reaches two main areas where endangered species are found in the basin – barrier islands and the river’s southernmost Birdfoot Delta.

“These areas are projected to have slight decreases in sediment and PFAS due to the project,” said the request written by National Marine Fisheries Service marine biologist Rachel Sweeney. “Therefore, it is likely that ESA-listed species will experience no change or decreases in PFAS compound exposures due to the MBSD Project.”

"A portion of the PFAS compounds will likely behave similarly to fine sediments and be incorporated into the delta building area – an area where ESA listed species are less likely to occur,” she said.

Similar language appeared in the Fish & Wildlife Service note.

Both included a May report produced by Seattle-based Confluence Environmental Co. for NOAA and the Louisiana Trustee Implementation Group.

That report pointed out that the new EPA PFAS regulatory standards were not in place when biological opinions were created by the two federal agencies for the diversion project, and said it’s anticipated that scientific findings about the chemicals will continue to evolve, thanks to additional research already underway.

But it also said that the levels of PFAS concentrations in the river at New Orleans are between 8.1 and 11 parts per trillion, while EPA’s proposed limits for amounts that threaten aquatic life through chronic exposure are between 8,400 and 94,000 ppt, and limits for acute exposure between 3 million and 49 million ppt, depending on the PFAS compound.

Both federal agencies said they were also requesting the additional review, in part, because they have added more endangered and threatened species in the region since the initial reports were released in 2021.

The endangered species potentially at risk now include pallid sturgeon, giant Manta ray, and West Indian manatee; eastern black rail, piping plover, and red knot shorebirds; and green, hawksbill, Kemp’s ridley, leatherback, and loggerhead sea turtles and the alligator snapping turtle. Both queen conch, found in the Flower Garden Banks National Marine Sanctuary in the Gulf of Mexico off the Louisiana-Texas border, and the Rice’s whale, also found in the Gulf, are both too far away from the diversion to be affected.

Both letters say that if the re-initiation of the endangered species consultation is granted, until it’s completed, the Louisiana trustees “will not make any irreversible or irretrievable commitment of resources with respect to the MBSD Project" that would preclude alternatives eventually being adopted to comply with federal law.

The trustees have the authority and funding necessary to modify the project to minimize impacts to species, the letters said, but both concluded no changes would be necessary.

The opponents who filed suit against the project in January, including Jurisich Oysters, AmeriPure Processing, Matthew Tesvich, and the Earth Island Institute, sent a letter to the federal agencies and the Louisiana Coastal Protection and Restoration Authority on Nov. 8 charging that because of the potential exposure from PFAS compounds and other contaminants in the river, the project violated the Endangered Species Act. It demanded all work be halted immediately.

Elizabeth Lewis, an attorney representing the opponents, said site preparation work still underway violates the Endangered Species Act because it could preclude alternatives to the project.

“By conducting these activities, CPRA appears to be ‘steamrolling’ the project before the services have had an opportunity to fully evaluate adverse project impacts and potential alternatives,” she said. “Otherwise, there would be no reason for CPRA to embark on these activities prior to lawfully concluding consultation under the ESA.”

Officials with the National Marine Fisheries Service and Fish & Wildlife Service refused to say whether the re-initiation requests were being acted upon. A spokesperson for the Fish & Wildlife Service declined comment because the request “is associated with active litigation.”

A spokesperson for the the Army Corps of Engineers’ New Orleans District office, which issued the permits approving construction of the project, said it was up to the other federal agencies to notify it of any updates in their biological opinions. A spokesperson for the CPRA also said it would be up to the federal trustees to determine whether the re-initiation process would be approved.

Meanwhile, the diversion’s construction remains on hold, other than storage and other minor site work, due to a dispute between the state and Plaquemines Parish, which opposes the project. The parish has filed a lawsuit arguing the state should have obtained construction permits from it.

Gordon “Gordy” Dove, who chairs the CPRA board of directors, has said the state is in the midst of talks with the parish that include possible changes to its design, but has refused to say whether those changes include major reductions in the amount of water the diversion would move into the basin.

The Senate Transportation Committee is expected to review the status of the diversion at a Thursday morning meeting.

Email Mark Schleifstein at or follow him on Twitter, @MSchleifstein. His work is supported with a grant funded by the Walton Family Foundation and administered by the Society of Environmental Journalists.